Low voltage driving of STN LCDs with low hardware complexity for portable applications

Abstract

In passive matrix liquid crystal displays (PMLCDs), multiplexing is achieved by using intrinsic non-linear electro-optic characteristics of the displays. Supply voltage can be reduced considerably as compared to the conventional as well as multi-line addressing techniques by using displays with steep electro-optic characteristics. The technique is demonstrated by driving a display with the hybrid addressing technique (HAT) that has a low hardware complexity. A 35% reduction in supply voltage is achieved by using a display with steeper electro-optic characteristics than necessary for the application. The technique can be extended to display gray scales in combination with the successive approximation approach by using five multiplexers and a few voltage level generators (VLG) that are common to all the drivers in the display. It is a simple solution to reduce the hardware complexity, supply voltage and cost.